Of course, repeated cdr ing on the original list will just give you the original cdr since the function does not change the list. You need to evaluate the cdr of the cdr and so on. If you continue this, eventually you will be returned an empty list, which in this case, instead of being shown as is shown as nil. In this case, the Lisp interpreter evaluates the innermost list first. The innermost list is quoted, so it just passes the list as it is to the innermost cdr. This cdr passes a list made up of the second and subsequent elements of the list to the outermost cdr , which produces a list composed of the third and subsequent elements of the original list.
In this example, the cdr function is repeated twice and returns a list that consists of the original list without its first two elements. The nthcdr function does the same as repeating the call to cdr. In the following example, the argument 2 is passed to the function nthcdr , along with the list, and the value returned is the list without its first two items, which is exactly the same as repeating cdr twice on the list:.
Using the original four element list, we can see what happens when various numeric arguments are passed to nthcdr , including 0, 1, and It is worth mentioning that nthcdr , like cdr , does not change the original list--the function is non-destructive.
This is in sharp contrast to the setcar and setcdr functions. As you might guess from their names, the setcar and setcdr functions set the car or the cdr of a list to a new value.
They actually change the original list, unlike car and cdr which leave the original list as it was. One way to find out how this works is to experiment.
We will start with the setcar function. First, we can make a list and then set the value of a variable to the list, using the setq function. Here is a list of animals:. If you are reading this in Info inside of GNU Emacs, you can evaluate this expression in the usual fashion, by positioning the cursor after the expression and typing C-x C-e.
I'm doing this right here as I write this. This is one of the advantages of having the interpreter built into the computing environment. When we evaluate the variable animals , we see that it is bound to the list giraffe antelope tiger lion :. Put another way, the variable animals points to the list giraffe antelope tiger lion. Viewed 74 times. Active Oldest Votes.
This is what I would do. Ok, will try to use your code even that it's completely different then my original code. I know that you can write completely different code than the one in answer. Also It will be problematic in the way you have structured your code because I can't run duplicate function in every function that process the nodes I need that data to be stored in data structure itself. Some may try that.
Others might suggest, "this radically different approach is a major improvement. I've come back to your recent questions several times and was chased off by the wall of code. Aadit was, and seems to have, at the very least, come up with a working solution.
ScottSauyet maybe it's working but it's hard to read and it seems of any use because it changed fundamental thing which is data structure that my code operate on. In previous question I was given answer with lazy evaluation and I've asked abut linked list, this type of answers are not real answers to me.
When I under the question I'm first try to solve the problem the OP have and not give wall of code that is completely different than my and of no use. Now place your cursor behind the closing bracket of the while expression and add another break point following the same method as above. With this in mind, let's add a watch to the index variable idx and the variable holding each line entity: ent.
The variable idx should now appear in the Watch Window list, with a value of nil since it is local to the program and does not hold a value until the relevant setq expression is evaluated in the code. With the Watch Window still open, double-click on any instance on the ent variable and click on the Add Watch button in the Watch Window the button with the glasses symbol :. This variable should also now appear in the list, also with a value of nil.
Switch to the AutoCAD window, and run the program once more by again typing linelen at the command-line. When the code evaluation reaches our first break point, code evaluation will be paused and the VLIDE Editor window will appear, highlighting the code between the two break points. From here, we have complete control over the code evaluation.
It takes one argument and returns t if the argument is a complex number otherwise it returns nil. It takes one argument and returns t if the argument is a character otherwise it returns nil. It takes one argument and returns t if the argument is a string object otherwise it returns nil. It takes one argument and returns t if the argument is an array object otherwise it returns nil.
It takes one argument and returns t if the argument is a package otherwise it returns nil. Previous Page.EPOS POSITION PAPER. European Position Paper on Rhinosinusitis and Nasal Polyps Wytske J. Fokkens, chair a, Valerie J. Lund, co-chair b, Joachim Mullol, co-chair c, Claus Bachert, co-chair d, Isam Alobid c, Fuad Baroody e, Noam Cohen f, Anders Cervin g, Richard Douglas h, Philippe Gevaert d, Christos Georgalas a, Herman Goossens i, Richard Harvey j, Peter Hellings k, Claire .